The present invention relates to an organic electroluminescent element (EL element) and an organic EL display using the same.
An organic EL element has features such as spontaneous emission (the backlight used in a liquid crystal element is not required) and high-speed response and its application to a flat panel display is expected.
In case of realizing a full color display panel using an organic EL element, it is required to prepare organic EL elements each emitting light of one of three primary colors (blue, green or red). For a red light emitting organic EL element, among these elements, a DCM pigment as described in C. W. Tang, S. A, Vanslyke, and C. H. Chen, Journal of Applied Physics, Vol. 65, 3610 (1989) has been used, however, further improvement in emission color and emission efficiency is required.
There is an example wherein a porphin or porphyrin compound capable of emitting red fluorescence is used as a light emitting material so as to obtain a red light emitting EL element (Japanese Unexamined Patent Publication (Kokai) No. 9-13024, Japanese Unexamined Patent Publication (Kokai) No. 9-296166, Japanese Unexamined Patent Publication (Kokai) No. 11-251061, Japanese Unexamined Patent Publication (Kokai) No. 11-251062, and Domestic Re-Publication of PCT International Application No. 98/000474).
Japanese Unexamined Patent Publication (Kokai) No. 11-144868 discloses a red light emitting organic EL element using a bisanthrene compound.
Furthermore, Japanese Unexamined Patent Publication (Kokai) No. 5-214334 discloses an organic EL element using zethrene or a derivative thereof, but does not disclose the use of, a monoarylaminozethrene or diarylaminozethrene compound as a zethrene derivative.
The traditional red light emitting EL elements are insufficient in emission efficiency and emission color purity as compared with blue and green light emitting EL elements and further improvement is required.
An object of the present invention is to provide a red light emitting organic EL element having high emission efficiency, and high color purity and an organic EL display using the same, by studying the light emitting material molecules contained in an organic EL element.
The present inventors have intensively studied the object described above and found that an organic EL element produced by using a certain monoarylaminozethrene or diarylaminozethrene compound as a light emitting material emits light with higher luminance as compared with the prior art.
It has also been found that the material has high carrier transporting properties, and that an organic EL element produced by using the material as a hole transporting material or an electron transporting material, and an organic EL element produced by using a thin film made of a mixture of the material and another hole transporting material or electron transporting material, also emit light with higher luminance as compared with the prior art.
The organic electroluminescent (EL) element of the present invention is an organic EL element having a positive electrode, a negative electrode, and an organic light emitting layer located between the positive electrode and the negative electrode, characterized by the material of the organic light emitting layer comprising an arylaminozethrene compound represented by the following general formula: 
wherein at least one of R1 to R14 is an arylamino group represented by the following structural formula: 
wherein R is a substituted or unsubstituted aromatic group having a single aromatic ring or a condensed aromatic ring with up to five rings, the substituent containing at least one kind of atoms selected from carbon, oxygen, nitrogen and sulfur atoms in case of the substituted aromatic group, the total numbers of atoms other than hydrogen in the substituted aromatic group being not more than 25, and Rxe2x80x2 is hydrogen, halogen, xe2x80x94OH, xe2x80x94OCH3, or an alkyl group having 1 to 10 carbon atoms, and, when the arylaminozethrene compound includes two or more arylamino groups, they may be the same or different, and groups other than the arylamino group among R1 to R14 independently represents hydrogen, halogen, xe2x80x94OH, xe2x80x94OCH3, an alkyl group having 1 to 10 carbon atoms, or the substituted or unsubstituted aromatic group as aforementioned.
The present invention also provides an organic EL display using the organic EL element of the present invention.
More specifically, the organic EL display of the present invention includes a substrate, an organic EL layer including the organic EL elements of the present invention provided on the substrate, and a circuit for driving the organic EL elements included in the organic EL layer.